Modern vehicles, such as automobiles, are often equipped with electric power steering (EPS) systems. Generally, EPS systems use a motor to provide a vehicle driver with powered assistance with moving the steering rack and, in turn, angularly moves the wheels of the vehicle from a left-most position to a right-most position.
In different maneuvering situations, the EPS motor will draw different amounts of power from the battery and the vehicle's electrical system based upon the steering demand and the load on the wheels. For example, during low speed maneuvers the EPS motor will require more current to drive more torque to the steering rack than during high speed maneuvers.
As the wheels move from the left-most position to the right-most position, the steering rack moves linearly through its range of motion such that the length of the steering rack extending outwardly on each side of the steering gear changes. Equating the steering gear to a fulcrum and the portion of the steering rack extended outwardly from the steering gear to a lever arm, as the linear position of the steering rack changes, so does the magnitude of the radial forces exerted on the steering rack. For example, when the wheels are in the left-most position, one side of the steering rack will be fully extended outwardly from the steering gear. Conversely, when the wheels are in the right-most position, the same side of the steering rack will be minimally extended from the steering gear. When the steering rack is fully extended to either side of the steering gear, the steering rack is more susceptible to damage.
When the front suspension is near or at its maximum upward or downward travel, the steering tie rod is forced to have an extreme angle with respect to the rack bar. The steering tie rod transmits force from the rack bar to the suspension or vice versa and is generally coaxial to the rack bar during high force parking lot steer maneuvers. When the vehicle passes over an obstacle like a rock while traveling off road, the front suspension is compressed to nearly the limit. During such incident, if the steering rack is fully extended under the full power of the motor and vehicle operator, resultant bending stress may damage the steering rack bar.
Accordingly, it is desirable to provide systems and methods for controlling the EPS motor to prevent damage to components of the EPS. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.